How Tunas and Lamnid Sharks Swim: An Evolutionary Convergence

Both tunas and lamnid sharks, including makos and whites, are top
predators and have similar streamlined body shapes. And the
similarity between these fishes, it turns out, is more than skin
deep. The two groups have developed high-speed swimming techniques
that involve efficient movements of only their tail sections, rather
than the full-body undulations of most fish. They accomplish this by
keeping their red muscle in their torsos and transferring the muscle
force to the tail through large, specialized tendons. While the two
groups' common ancestor diverged more than 400 million years ago,
selection pressures seem to have made both fish hit upon nearly
identical movement mechanisms.